International Journal of Engineering and Techniques - Volume 3 Issue 5, Sep - Oct 2017 ISSN: 2395-1303 http://www.ijetjournal.org Page 183 Numerical Analysis of the Effect of Static Mixer on SCR System Performance of Marine Diesel Engine Jaedaa Abdulhamid 1 , Prof. T.V.K.Bhanuprakash 2 , Prof. P.V.J. Mohan Rao 3 1,2 (Department of Marine Engineering, A.U. College of Engineering, Andhra University, Visakhapatnam 530017) I. INTRODUCTION Over 90% of global trade is carried by ship industry all over the world [1]. It is the most safe and cost effective method for long distance transportation. On the other hand, Maritime sector accounts for up to 30% of the annual global NO x emissions which are considered a major air pollution problem that threatens human health and environment [2]. They contribute to acid rain formation and photochemical smog which can damage crops, forests, wildlife populations, and cause respiratory illnesses. Marine vessels are also an important source of GHG emissions which contribute to climate change [3]. Shipping emissions are expected to double by 2050 and harmful effects will continue to rise [4]. Therefore, IMO assigned limits on the permissible amounts of NO x emissions in three standards namely Tier I, Tier II and Tier III. Tier III standard entered into force after 1st January 2016 and it is the strictest regulation where 80% NO x reduction efficiency is required [5]. In order to comply with these regulations, efforts were made to develop NO x after-treatment technologies such as SNCR (selective non catalytic reduction), LNT (Lean NO Trap Catalyst), and plasma-facilitated catalysis (PFC). Among all these technologies, selective catalytic reduction (SCR) is the most preferred mainstream technology for NO x emissions RESEARCH ARTICLE OPEN ACCESS Abstract: Due to increasing awareness of negative impacts of emissions of NO x on public health and the environment, IMO has issued stringent rules to reduce NO x emissions from marine vessels.Tier III is the most stringent standard where around 80% NO x reduction efficiency is required. In order to satisfy these rules, NO x abatement technologies were developed and SCR is considered one of the most effective and promising methods to meet such regulations.In the current work, SCR system is fitted to a medium speed marine diesel engine and UWS is centrally injected from 6-hole nozzle positioned 5D upstream of SCR entrance. Two different types of static mixers are installedupstream of SCR entrance namely blade mixer and flapper mixer to investigate their effect on two parameters namely urea conversion efficiency and uniformity index (UI).Four different configurations are investigated and compared to each other'sas listed in table 1. These four cases are researched at three different exhaust gas velocities. Results revealed that the best urea conversion efficiency is achieved when both mixers are installed with a value of91.7%, while flapper mixer resulted in 10.86% higher urea conversion efficiency over the blade mixer. The reason behind this is due to the bigger contact surfaces between exhaust gas flow and flapper mixer, more ammonia and flow come in touch with each other's leading to better mixing quality.UI increases along with urea conversion and the maximum value achieved is 92.8% at 8.3 m/s when both mixers are installed. On the other hand, flapper mixer achieved 91.9% UI which is 2.79% higher than that achieved by blade mixer.At smaller exhaust velocities, higher UI and higher urea conversion efficiency are achieved due to more residence time which enhances mixing and chemical reactions. Keywords — Static mixer, SCR, Performance,Marine diesel engine, Urea conversion, UI.